Interpretive Summary: Disposal of subsurface drainage water from irrigated agricultural lands is a major problem which must be managed if irrigated agriculture is to survive. In addition to salts, drainage water may contain trace elements such as boron and selenium which has been shown to have severe adverse impacts on the environment. As the permissible concentration of salt and other elements are lowered, irrigation district managers will have to aggressively manage the discharge of drainage water to meet load and concentration restrictions of salt and other elements. To do this, they will have to quantify the discharge and load from each drained area of the district. Using these data they can select areas to focus the initial improvements. This paper describes a system which ranked each drainage sump by area drained, total drainage flow, irrigation efficiency, and salt load per unit area and calculated a composite value for a final ranking. The results demonstrated that no single factor dominated the selection.

Technical Abstract:
An irrigation district on the west side of the San Joaquin Valley of California was used to demonstrate a method for selecting areas for improvement of irrigation and drainage water management. Improved management should result in reduced drainage water volumes and salt loads. Factors considered included area drained, total drainage flow, irrigation efficiency, and salt load per unit area. The factors were used to rank each sump and then to calculate a composite value for the final ranking. The results demonstrated that no single factor dominated the ranking and selection of a sump.